1. Field of the Invention
The present invention generally relates to a method for assembling an optical assembly comprising parts requiring relatively precise positioning, and more specifically to a method for efficiently assembling an optical transceiver module used to receive and transmit optical signals.
2. Description of Related Art
In optical communication systems, it is very important of an optical assembly for receiving and transmitting optical signals, and converting electrical signals into corresponding optical signals, and vice verse in an optical transceiver module. The optical assembly comprises parts which need precise positional alignment. Thus the assembling is relatively difficult. Therefore, a variety of methods for assembling have been developed.
The optical assembly comprises a support member having a first junction surface, and a cap member having a second junction surface. One conventional way to make the assembly is to secure the cap member to the support member by applying a heat curable adhesive, such as heat curable epoxy, between the junction surfaces. To ensure proper alignment between the support member and the cap member, during the process of assembling, the cap member and the support member are held in an adjusting device with the first junction surface engaging the second junction surface. A positional adjustment is performed on the support member and/or the cap member to obtain the desired alignment. The heat curable adhesive is then applied to the junction surfaces.
The optical assembly is securely clamped by a clamping device, and then moved into a curing oven to cure the adhesive. The entire process is unduly complicated.
Furthermore, such a method is not suitable for single mode fiber transmission systems because the diameter of a single mode fiber is between 6 xcexcm and 10 xcexcm. A 0.5 xcexcm relative displacement of assembled components may result in a poor transmission. While the clamped optical assembly is being moved into the curing oven, the assembly is vulnerable to impact or other unwanted force. This can result in relative displacement and thus poor alignment between components of the assembly. In addition, temperature gradient occurring during the curing process may cause non-uniform heating of the assembly. This can also result in displacement of components.
Another conventional method for assembling an optical assembly is disclosed in U.S. Pat. No. 4,969,702 (shown in FIG. 1). The optical assembly comprises a laser diode (LD) 12, a support member 14, a lens 16 and a cap member 18. The laser diode 12 is fixedly positioned in the support member 14 to generate light outputs at particular wavelengths. The lens 16 is positioned with respect to the laser diode 12. The cap member 18 has a through hole 22. An optical fiber 24 placed in a ferrule 26 is secured in the through hole 22. An ultraviolet curable (UV) epoxy is applied between the cap member 18 and the support member 14, with the optical fiber 24 in approximate alignment with the laser diode 12 and the lens 16. Thus light outputs of the laser diode 12 are coupled to the optical fiber 24 through the lens 16. The support member 14 and the cap member 18 are then placed in an adjusting device, for precise adjustment of the relative position of the cap member 18 and the support member 14. The assembly is then exposed to UV light to cure the epoxy. At least one of the components must be transparent, to ensure proper exposure of the epoxy to the UV light. Furthermore, the adjusting device must have a sophisticated design to ensure such proper exposure. Thus the material of the components and the design of the adjusting device are both restricted.
Still another conventional method for assembling an optical assembly is disclosed in U.S. Pat. No. 5,073,047 (shown in FIG. 2). The optical assembly comprises a light source 15, a holder 19, a housing 17 and a receptacle 1. The light source 15 is fixedly positioned in the holder 19. The holder 19 with the light source 15 therein and the housing 17 are solidly welded together by means of a laser beam 16. The housing 17 and the receptacle 1 are solidly welded together by means of a laser beam 18 after positional alignment. The components solidly welded by the laser beams 16, 18 must be made of metal, and a costly laser device must be used.
Yet another conventional method for assembling an optical assembly uses an instant glue in order to reduce costs. The method comprise the steps of placing a support member and a cap member in an adjusting device, operating the adjusting device to properly align the members, and applying an instant glue between the members. The instant glue solidifies quickly and joins the support member and the cap member together. However, the instant glue can solidify only when it contacts vapor. Since vapor concentration may vary from point to point in a three dimensional space, and since it is difficult to control vapor concentration, a non-uniform curing may occur. This can result in poor alignment between the two members.
In view of above-described drawbacks of the prior art, there is a great need to provide a method for efficiently and effectively assembling an optical assembly having parts requiring relatively precise orientations.
It is an object of the present invention to provide a method for efficiently and rapidly assembling an optical assembly having parts requiring relatively precise orientations.
In accordance with the present invention, a method for assembling an optical assembly comprising a base member having a first junction surface and a receptacle having a second junction surface is disclosed. The method comprises the steps of: providing a base member retaining a photoelectric component therein and having a first junction surface; providing a receptacle retaining an optical fiber therein and having a second junction surface; bringing the receptacle and the base member together so that the first and second junction surfaces engage each other; applying a heat curable adhesive between the junction surfaces; providing a heating device having a heat energy emitting part to surround the junction surfaces; and actuating the heating device to generate heat in the heat energy emitting part to heat and cure the heat curable adhesive, thereby securing the base member and the receptacle together. If desired, a cooling step may be performed after the heating step. The heating device may comprise an electric heating element, such as a resistance wire. Alternatively, the heating device may comprise piping for directing heated air streams toward the adhesive.